The transcutaneous transfer of a chemical, i.e., the transfer of a chemical into the skin of a patient, is widely used in drug delivery applications. A number of transcutaneous delivery systems are known. Perhaps the simplest involves placing the chemical to be delivered in contact with the patient's skin and allowing the chemical to penetrate the skin by osmosis and related spontaneously occurring mass transport phenomena. This technique is the most common one for applying various cosmetic lotions, such as skin softeners and the like, to the skin. The lotion is simply spread on the skin and is allowed to remain there, enabling some components of the lotion to penetrate the skin.
A more sophisticated transcutaneous chemical delivery technique, known as iontophoresis, uses electrical energy to induce the chemical to penetrate the skin. Iontophoresis allows better control of the rate of delivery of the chemical and of the depth of penetration of the chemical into the skin. Furthermore, iontophoresis enables larger molecules to penetrate the skin.
Stripped to its bare essentials, iontophoresis involves the application of an electromotive force to drive ionic chemicals into the skin. An iontophoretic device includes two electrodes. At any one time, one of the electrodes has in its vicinity the ionic species to be driven into the skin. The other electrode serves to close the electrical circuit through the skin. In use, both electrodes are brought into contact with the skin. An electromotive force is applied to the electrodes, creating an electrical circuit between the two electrodes which runs through the skin and which drives the ionic chemical species away from the first electrode and into the skin.
Biomedical electrodes for sensing biomedical signals such as those used in measuring electrocardiographic (EKG) or electroencephalagraphic signals are known. Moreover, electrodes for passive sensing of transcutaneous electrical currents, or for introducing electrical energy transcutaneously, are known.
None, however, are optimal for providing an even current distribution across the electrode. In certain applications, it is desirable to have even current distribution or potential across the electrode. This is accomplished by providing an electrode that exhibits high conductivity and low resistance. At present, there are no electrode that exhibit these qualities.
In addition, none of the existing electrodes are optimal for use in areas of the body where skin depth changes and sensitivity to electrical current vary across any given area of the body. Such an electrode or device should have even current distribution as well as low resistance in certain areas to avoid harming the more sensitive areas of the skin surface through burning or electrolysis. Moreover, none of the existing electrode technology is optimal for use in contoured areas of the body where there are high concentration of nerve endings, such as the face, hands, feet, or head. In such cases where there are high concentrations of nerve endings there is an increased possibility from the existing devices for sensitivity to iontophoresis.
There are also particular medicaments that may be most effectively delivered transcutaneously. For example, some acne medications are most effective when they are delivered directly into the skin's surface in the area in which the acne appears. These situations are ripe for iontophoretic delivery of such a medicament. Presently there are no electrodes, iontophoretic devices or methods that effectively deliver such agents through the skin without possibly harming the skin. There are no existing electrodes, or iontophoretic devices or methods that take into account the variations in skin sensitivity to the introduction of electric current from one area of the skin to another.
There are also situations where transcutaneous application of a particular medicament may be messy, or may require isolation of the area during treatment of that area. For example, nail fungal treatments must be applied directly to the toe or finger nail. During such treatments, the patient may want to isolate such medicament while the treatment is in progress. In such cases, it is preferable that the electrodes or iontophoretic device be completely disposable, as well as capable of conformation to the applicable contours of the body. In addition, the electrodes and device should be capable of isolating such an area during treatment to decrease the spread of any medicament or condition to other areas, clothing or the like. To be completely disposable and conformable, such a device must be flexible, relatively thin and be made of inexpensive materials. At present, there are several patents directed to disposable electrodes. However, none of the prior art disclosed a disposable electrode for use in iontophoresis where the electrode has varied resistivity to provide for a predetermined level of current distribution and to compensate for variations in the sensitivity of certain skin areas and thus avoid harmful burning.
Thus, there is a widely recognized need for, and it would be highly advantageous to have, an electrode that is optimized both compositionally and structurally to minimize or eliminate irritation to the user's skin.
There is a further need for an iontophoretic device and method that utilize electrodes that are optimized both compositionally and structurally to minimize or eliminate irritation to the user's skin.
There is another need for an electrode that varies the resistance across the area of the electrode to compensate for variations in skin sensitivity.
There is yet a further need for an iontophoretic device and method that incorporates at least one electrode that varies the resistivity across the area of the electrode to compensate for variations in skin sensitivity.
There is still a further need for an electrode that is flexible and disposable, and that is varied in thickness across the area of the electrode so as to vary the resistivity and avoid harmful burning to sensitive skin areas.
There is yet another need for a method of introducing an agent into the skin where the electrode receiving the current has a varied resistance so that the agent may effectively pass into the skin yet avoid burning or otherwise harming the skin.
There is still a further need for a device and method that effectively eliminates cellulite below the skin surface by introducing current to the skin via an electrode where the electrode has a varied thickness across the area of the electrode.